linux-kernel - Re: [PATCH] xen-netfront: Fix Rx stall during network stress and OOM

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Date:   Thu, 12 Jan 2017 15:17:06 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     vineethp@...zon.com
Cc:     boris.ostrovsky@...cle.com, jgross@...e.com,
        xen-devel@...ts.xenproject.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, kamatam@...zon.com,
        aliguori@...zon.com
Subject: Re: [PATCH] xen-netfront: Fix Rx stall during network stress and
 OOM

From: Vineeth Remanan Pillai <vineethp@...zon.com>
Date: Wed, 11 Jan 2017 23:17:17 +0000

> @@ -1054,7 +1059,11 @@ static int xennet_poll(struct napi_struct *napi, int budget)
>  		napi_complete(napi);
>  
>  		RING_FINAL_CHECK_FOR_RESPONSES(&queue->rx, more_to_do);
> -		if (more_to_do)
> +
> +		/* If there is more work to do or could not allocate
> +		 * rx buffers, re-enable polling.
> +		 */
> +		if (more_to_do || err != 0)
>  			napi_schedule(napi);

Just polling endlessly in a loop retrying the SKB allocation over and over
again until it succeeds is not very nice behavior.

You already have that refill timer, so please use that to retry instead
of wasting cpu cycles looping in NAPI poll.

Thanks.